While the original question mentions Google specifically, it's important to note that the Google WebMaster Tools would only block Google. Adding the Disallow rules in the robots.txt file would address other search engines as well.
– Matt V.Jan 14 '13 at 20:37

1

True. It should also be clarified that robots.txt does not stop Google indexing pages but stops it reading their content. The best solution is using the robots meta tag on the page itself. This is supported by all systems.
– Tony McCreathJan 15 '13 at 14:35